Background: PN is the preferred treatment for Stage T1 kidney tumors as studies show favorable long-term tumor control and benefits to nephron preservation. Intraoperative FSA is frequently performed during PN to ensure complete tumor resection. We investigate the utility of routine FSA during PN by evaluating its impact on final SM status and, more importantly, on long-term prognosis.Design: We retrospectively reviewed the data from a consecutive series of patients (n=433) who underwent PN (n=447) for a suspected renal tumor at our institution from 2004 to 2012. The lesions included 338 renal cell carcinomas (RCCs) [240 clear cell RCCs (CCRCCs), 77 papillary RCCs (PRCCs), 18 chromophobe RCCs, 3 other RCCs], 2 metastatic tumors, 73 other renal neoplasms, and 34 other benign conditions.Results: FSA was performed in 293 (68%) patients/300 (67%) PNs respectively, while no FSA was done in 140 (32%) patients/147 (33%) PNs. Positive SMs (+SMs) were found significantly more often (p<0.001) in the no FSA group (18%) than in the FSA group (4%). There were also significant correlations between FSA and SM status in subgroups of patients: all RCCs (p<0.001), CCRCCs (p<0.001), PRCCs (p=0.014), pT1 tumors (p<0.001), exophytic (p<0.001) and endophytic (p=0.011) tumors, Fuhrman grades 1-2 (p<0.001) and 3-4 (p=0.040) tumors, and upper (p<0.001) and mid (p=0.026) pole tumors. Final SMs were less likely to be positive if more than one FSA were sent compared to when only one FSA was sent (p=0.036). There were 11 tumor recurrences during follow-up (mean: 24.6; range: 1-92 months); 6 (2%) in the FSA group and 5 (4%) in the no FSA group (p=0.340). Neither FSA diagnosis (p=0.436) nor final SM status (p=0.295) was significantly associated with long-term outcomes. Kaplan-Meier analysis in RCC cases revealed that, overall, FSA did not considerably contribute to preventing recurrence (p=0.111). However, FSA significantly improved outcomes in patients with pT1 tumors (p=0.007), but not ≥pT2 tumors (p=0.475). Performing FSA strongly correlated with better outcomes in patients with exophytic tumors who underwent PN laparoscopically (p=0.011). No impact of FSA on recurrence was seen in patients with different locations, histologic types, and Fuhrman grades.Conclusions: Although FSA overall reduces the risk of +SM, our data argues against routine FSA during PN as long-term outcomes are not affected by FSA. Longer follow-up times may be needed to confirm our findings. FSA may, however, be useful in select patients who have pT1 and/or exophytic tumors.Category: Genitourinary (including renal tumors)